Under the contract, Telstra will provide telecommunications and managed services covering CBA branches, contact centres, the EFTPOS network and non-branch ATMs.
The contract also covers provision of "converged communications", according to a statement released by both companies today.
Telstra will supply services running off both its Next IP and Next G networks.
The contract is worth up to $100 million per year over ten years to Telstra and forms part of the CBA's smart sourcing strategy, the bank said.
Gen-i previously held the contract for managing network services for CBA.
It will "continue to work on a range of network services and remains a strategic support to [CBA]", the bank said.
CBA CIO Michael Harte said choosing a new partner for the provision of telecommunication services was a strategic part of its network upgrade.
"Our arrangement with Telstra is a partnership which is directly focused on customer satisfaction through well-defined shared goals, commitments and business outcomes," he said.
"This is the first time we have struck a deal of this kind."